Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.31	3.836%	$168.5362	$168.54	$168.55	$168.50
Purchase #2	$40.54	11.282%	$45.1137	$45.11	$45.10	$45.10
Purchase #3	$99.27	12.432%	$111.6112	$111.61	$111.60	$111.60
Purchase #4	$232.99	13.344%	$264.0802	$264.08	$264.10	$264.10
Purchase #5	$244.72	8.621%	$265.8173	$265.82	$265.80	$265.80
Purchase #6	$161.57	10.557%	$178.6269	$178.63	$178.65	$178.60
Purchase #7	$136.55	9.655%	$149.7339	$149.73	$149.75	$149.70
7 purchase totals =	$1,077.95		$1,183.5194	$1,183.52	$1,183.55	$1,183.40